<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <button @click="changePic">变美女</button>
        <hr>
        <img :src="pic" alt="">
    </div>

    <script src="./vue.js"></script>
    <script>
        new Vue({
            el: '#app',
            data() {
                return {
                    pic: './images/boy.png'
                }
            },
            methods: {
                changePic () {
                 if (this.pic.indexOf('boy') !== -1) {
                    // 把pic改了
                    this.pic = './images/girl.png'
                 }else {
                    this.pic = './images/boy.png'
                 }
                }
            }
        })
    </script>
</body>
</html>